Electrodeposition of cobalt

ABSTRACT

A PROCESS FOR THE ELECRTRODEPOSITION OF BRIGHT COBALT OR COBALT-NICKEL ALLOY ELECTROPLATES CONTAINING AT LEAST 50% COBALT IN WHICH THE AQUEOUS COBALT PLATING BATHS FROM WHICH THE ELECTROPLATES ARE DEPOSITED CONTAIN AT LEAST 0.05 MILLOMLES PER LITER OF A BRIGHTENER HAING THE FORMULA:   H-(O-CH(-R)-CH2)M-O-CH2-C*C-CH2-O-(CH2-CH(-R)-O)N-H   WHEREIN M IS A NUMBER FROM 1 TO 4, N IS A NUMBER FROM 0 TO 4, R IS HYDROGEN OR A CH2R, GROUP IN WHICH R&#39;&#39; IS A CHLORO, HYDROXY OR SULFONIC GROUP.

United States Patent Q 3,814,674 ELECTRODEPOSITION F COBA LT Norman C. Adamowicz, Inkster, Roy W. Klein, St. Clair Shores, Robert A. Tremmel, Wyandotte, and Richard J. 'Clauss, Allen Park, Mich., assignors to Oxy Metal Finishing 'Corporafion, Warren, Mich. No Drawing. Filed Nov. 5, 1970, Ser. No. 87,322

Int. Cl. C23b 5/08, 5/32 US. Cl. 204-43 T Claims ABSTRACT OF THE DISCLOSURE A process for the electrodeposition of bright cobalt or cobalt-nickel alloy electroplates containing at least 50% cobalt in which the aqueous cobalt plating baths from which the electroplates are deposited contain at least 0.05 millimoles per liter of a brightener having the formula:

wherein m is a number from 1 to 4, n is a number from 0 to 4, R is hydrogen or a CH R' group in which R is a chloro, hydroxy or sulfonic group.

This invention relates to an improved process for the electrodeposition of bright cobalt and cobalt-nickel alloy electroplates containing at least 50% cobalt and more particularly, it relates to an improved brightening additive for use in the plating baths from which such electroplates are deposited.

The use of nickel electroplates to provide decorative and/or protective coatings on various substrates is well known. Heretofore, numerous processes and electroplating baths have been developed for the electrodeposition of nickel for these purposes. Although it is known that electrodeposits of cobalt possess many of the same desirable qualities as nickel electrodeposits, comparatively little work has been done to develop commercial processes and electroplating baths for the electrodeposition of cobalt, principally because the price of cobalt and cobalt salts have always been appreciably higher than that for nickel. Recently, however, for various reasons, nickel and nickel salts have been in relatively short supply and, as a result of these shortages, the prices of these commodities have increased to the extent that in many instances, the use of cobalt electrodeposits have become economically feasible. In attempting to develop commercially practical processes for the electrodeposition of cobalt, however, it has been found that in many instances, the additives, such as brighteners and the like, and the processing techniques which, have heretofore been used in the nickel electroplating processes, have not necessarily been successful in cobalt processes, notwithstanding the chemical and physical similarities of these two materials.

It is, therefore, an object of the present invention to provide an improved process for the electrodeposition of bright cobalt and cobalt-nickel electroplates containing at least 50% by weight cobalt.

A further object of the resent invention is to provide an improved electroplatinfiaath from which bright cobalt and cobalt-nickel alloy electroplate may be deposited.

Another object of the present invention is to provide an improved brightening additive for use in electroplating Patented June 4, 1974 baths for the deposition of cobalt and cobalt-nickel alloy electroplates.

These and other objects will become apparent to those skilled in the art from the description of the invention which follows.

Pursuant to the above objects, the present invention includes a plating bath for the electrodeposition of cobalt which comprises an aqueous solution of at least one cobalt salt and, as a brightener, at least 0.1 millimoles per liter of a compound having the formula:

wherein m is a number from 1 to 4, n is a number from 0 to 4, .R is hydrogen or a CH R' group in which R is a chloro, hydroxy or sulfonic group. From this bath, there is electrodeposited a full bright cobalt plate over a wide range of current densities.

More specifically, in the practice of the present invention, the electroplating baths used are aqueous solutions containing one or more cobalt salts. Typically, such baths may be prepared by dissolving cobalt chloride and/or cobalt sulfate and boric acid in water. Other cobalt electroplating baths based on cobalt sulfate, cobalt chloride, cobalt formate, cobalt sulfamate, cobalt fluoroborate, or the like, as the cobalt salt dissolved in the aqueous acidic solvent, may also be used. Additionally, the electroplating baths of the present invention may also contain one or more nickel salts, of the same or similar type as the cobalt salts which have been indicated above. Where the electroplating baths used contain nickel salts in addition to the cobalt salts, the relative amounts of these should be such that the resulting cobalt-nickel electroplate produced contains at least about 50% cobalt.

These cobalt electroplating baths will contain a brightening amount of a compound having the formula:

H 0 bnom o-cm-oso-om-oombno current densities. Typically, these materials will be present in an amount within the range of about 0.05 to millimoles per liter of the plating solution, with amounts within the range of about 0.1 to millimoles per liter being preferred. This is not to say, however, that amounts of this brightening agent which are outside of these ranges may not be used but, rather, that for many typical operations with the process of the present invention, these amounts have been found to be preferred. It has further been found, however, that although amounts in excess of these preferred amounts may be used without detrimental etfect on the plating bath, there has generally not been found to be any advantage in using appreciably more than about 100 millimoles per liter of this brightening agent.

As is known in the art, these brightening additives may be prepared by the addition of 2-butyne-1,4-diol to an epoxide which addition is preferably base-catalyzed. Suitable epoxides which may be reacted with diol are selected from ethylene oxide, epichlorohydrin and the like. Where epichlorohydrin is used, the resulting adduct may be further treated to eifect partial or complete sulfonation or hydrolysis of the active chlorine, if desired. Typically, the reaction of the epoxide and the diol is carried out in a mole ratio of about 1-8z1 with the mole ratio of about 1- 2:1 being preferred. Although, as has been indicated, this reaction is preferably base-catalyzed, the reaction may be carried out in either a neutral or acid medium. In the latter types of reactions, however, the control of the reaction mechanism to produce the desired product may be more diflicult than with a base-catalyzed reaction and, for this reason, the former type of reaction is preferred.

In the preferred operation of the electroplating baths of the present invention, in addition to the brightening agent described above, these baths also desirably contain, as additional brighteners, an organic or sulfonic acid compound selected from yinyl sulfonic acid, 3-chloro-2-butene sulfonic acid and allyl sulfonic acid, either as such or as the salts thereof, and/or orthosulfobenzimide, either as such or as the salt. When these additional brightening agents are used, the organic sulfonic acid compound, preferably as the sodium salt, such as sodium allyl sulfonate, is desirably present in an amount within the range of about 0.5 to 10 grams per liter while the orthosulfo benzimide (saccharin) is desirably present in an amount within the range of about 0.5 to 6 grams per liter.

In formulating the electroplating baths for use in the method of the present invention, an aqueous acidic solution is formed containing the desired cobalt or cobalt and nickel salts. Typically, these electroplating baths will have a pH within the range of about 2 to 4.5 and, depending uponthe particular cobalt salts used, will contain the cobalt salts in amounts within the range of about 75 to 400 grams per liter. Where nickel salts are also present in the electroplating baths, these will typically be present in amounts within the range of about 5 to 250 grams per liter, depending upon the particular salt used as well as the amount of the cobalt salt which is present. In the most preferred plating baths which will also contain boric acid, this material is desirably present in amounts within the range of about 30 to 65 grams per liter.

In the operation of the processes of the present invention, the electroplating solutions will typically be used at a temperature within the range of about 40 to 65 degrees centigrade. In general, agitation of the solution, either by air agitation, cathode rod agitation, mechanical agitation or the like, is preferred. Although with the electroplating baths of the present invention, full bright cobalt electrodeposits are obtained over a broad current density range, e.g., 2 to 200 amps per square foot, the typical average current densities used in the operation of the process are within the range of about 30-50 amps per square foot, with plating times of from about 5 to 30 minutes. When operating in this manner, excellent full bright, ductile electrodeposits of cobalt and cobalt-nickel alloys containing at least 50% cobalt are obtained, which electrodeposits are found to be comparable to nickel electrodeposits in terms of their decorative and/or protective characteristics.

In order that those skilled in the art may better understand the present inventoin and the manner in which it may be practiced, the following specific examples are given. In these examples, unless otherwise indicated, parts and percent are by weight and temperatures are in degrees centigrade. It is to be appreciated, however, that these examples are merely exemplary of the present invention and are not to be taken as a limitation thereof.

EXAMPLE 1 A series of aqueous electroplating solutions were formulated containing 100 grams per liter CoCl -6H O, 60 grams per liter H BO 25 to 200 milligrams per liter of the ethylene oxide adduct of butyne diol (1.821 mole ratio), 0.5 to 5 grams per liter sodium allyl sulfonate and 3 to 5 grams per liter sacchrin. These solutions were maintained at a pH within the range of 2.5 to 3.5 and a temperature of from about 50 to 55 degrees centigrade. The solutions were agitated by means of air, cathode rod and mechanical agitation. Steel cathodes were plated in these plating baths, containing the varying amounts of the brightening additives, for 10 minutes at a current density of 35 amps per square foot and in each instance, a full bright cobalt electroplate was formed.

EXAMPLE 2 A series of aqueous electroplating solutions were formulated containing 150 grams per liter NiSO '7H O', 150 grams per liter CoSO -7H O, 45 grams per liter NiCl 6H O and 60 grams per liter H BO To these electroplating baths were added, as brightening additives, from 25 to 200 milligrams per liter of the epichlorohydrin adduct of butyne diol (1.2:1 mole ratio) which adduct had subsequently been reacted with sodium sulfite to effect replacement of Cl groups with SO Na groups. Additionally, the solutions contained from 0.5 to 5 grams per liter of sodium allyl sulfonate and 3 to 5 grams per liter saccharin. These plating baths were operated in the same manner as in Example 1 and in each instance a full bright cobalt-nickel alloy electroplate was produced over a current density range of from 3 to 150 amperes per square foot.

While there have been described various embodiments of the invention, the compositions and methods described are not intended to be understood as limiting the scope of the invention as it is realized that changes therewithin are possible and it is further intended that each element recited in any of the following claims is to be understood as referring to all equivalent elements for accomplishing substantially the same results in substantially the same or equivalent manner, it being intended to cover the invention broadly in whatever form its principle may be utilized.

What is claimed is:

1. A process for producing a bright cobalt deposit which comprises electrodepositing bright cobalt on a base metal from an electroplating bath comprising an aqueous acidic solution of at least one cobalt salt and a brightening amount of a compound having the formula:

wherein m is a number from 1 to 4, n is a number from O to 4, R is hydrogen or a CH R group in which R is a chloro, hydroxy or sulfonic group.

2. The process as claimed in claim 1 wherein the plating bath contains at least 0.05 millimoles per liter of the acetylenic compound.

3. The process as claimed in claim 2 wherein the plating bath contains at least one additional brightener selected from organic sulfonic acid compounds of the group allyl sulfonic acid, vinyl sulfonic acid and 3-chloro-2- butene sulfonic acid and ortho sulfobenzimide and salts thereof.

4. The process as claimed in claim 3 wherein the acetylenic brightener is present in an amount within the range of about 0.05 to millimoles per liter, the sulfonic acid brightener is present in an amount within the range of about 0.5 to 10 grams per liter and the sulfobenzimide brightener is present in an amount within the range of about 0.5 to 6 grams per liter.

5. The process as claimed in claim 4 wherein the additional brightener is selected from allyl sulfonic acid and its salts and orthosulfobenzimide and its salts.

6. The process as claimed in claim 5 wherein the plat- 3,002,902 10/1961 Foulke et a1. 20449 ing bath used also contains at least one nickel salt and 3,041,256 6/1962 Kleiner et a1 20449 the electrodeposit produced is a cobalt-nickel alloy con- 3,152,975 10/1964 Kardos et a1 20449 taining at least 50% cobalt.

7. The process of claim 1 wherein R is CH R'. 6 OTHER REFERENCES 8. The process of claim 7 wherein R is chloro. M l i i hi 43 November 19 9 The Process of claim 7 wherein is a Sulfomc Frederick A. Lowenheim: Modern Electroplating, P- pp. 468470 (1968).

10. The process of claim 7 wherein R is hydroxy.

10 GERALD L. KAPLAN, Primary Examiner US. Cl. X.R.

References Cited UNITED STATES PATENTS 3,366,557 1/1968 Foulke et a1. 20449 2,800,440 7/1957 Brown 20449 

